In today's business and scientific world, color has become essential as a component of communication. Color facilitates the sharing of knowledge and ideas. Companies involved in the development of digital color print engines are continuously looking for ways to improve the total image quality of their products. One of the elements that affects image quality is the ability to consistently produce the same quality image output on an imaging device or printer from one day to another, from one week to the next, month after month. There has been a long felt commercial need for efficiently maintaining print color image quality and predictability, particularly as electronic marketing has placed more importance on the accurate representation of merchandise in illustrative print or display media.
Digital color printers are capable of high image quality printing with CMYK toner/ink (C=cyan, M=magenta, Y=yellow and K=black), and regularly detect the processing of the pages as either color (CMYK) or a monochrome (black only), then charge the printed pages at a cost of either a color or a monochrome price accordingly. Customers expect high image quality printing with low cost charging per page, particular for a neutral gray color job. Besides page level color or monochrome detection, a latest marketing push is to have a tiered color billing approach where customers are charged for the amount of color that is present on a page. For example, a customer will expect that a page with all or mostly neutral gray colors (with equal RGB value, R=red, G=green, B=blue) should be charged as monochrome instead of color because it is what they see on the display systems. At the same time, they expect high quality printing. However, certain digital color print engines, such as ink jet and solid ink jet print engines, do not provide an image quality of black ink/toner only printing as good as that of a composite black printing (printed with combinations of CMYK toner/ink). As a practical matter, the color printers either RIP (raster image process) and print neutral gray color job in black only and charge at monochrome price, or RIP and print in composite black and charge at the color price.
Where the overall print job will only involve a page of monochrome black only (K-only) or pages with mostly monochrome black and with very little color content, customers have an expectation that when the page of a print job is totally or mostly monochrome, K only, the cost of that page should be less than the cost of printing a page comprised of a lot of colors, CMYK. As a practical matter, most suppliers of color printers will regularly detect the processing of a color printed job as either a composite color (CMYK) or a monochrome black (K only), and will charge a customer less for printing a page of K-only. In addition, for an input job having all or mostly neutral gray color (R=G=B), customers may view the page as a monochrome gray job, even though it is actually printed a composite gray (C,M,Y,K) and will expect the lower billing rate for that page.
To meet the customer's expectation for color billing, RIP processing workflow in the printer can set the job as “print as K-only” as a default for pixels that are “True Gray” (K-only) or “RGB Neutral Gray” (composite black with equal RGB values), instead of actually printing a composite black for the input color. For this “print as K-only” mode, image quality degradation of tone and color hue match will occur. More particularly, when a job will contain a sweep of K-only or neutral gray color (R=G=B) to near neutral gray color (R=G=B) a mismatch will be more noticeable, since the near neutral gray colors is printed in a composite black while the neutral gray is printed as K-only.
Accordingly, there is a need for a system which can accommodate customer expectations of lower billing for neutral gray color page jobs without suffering image quality degradation to the extent that a customer will view the print system as having an inferior quality print job.